The present invention relates to a method and a system of communicating or transmitting control data among a plurality of equipments (e.g. computers and I/O devices) coupled to a common signal transmission line.
Heretofore, when control data is to be exchanged among equipments through a common transmission line, transmitting equipment transmits data having a destination address for specifying a receiving equipment added to the control data and the receiving equipment determines whether the destination address specifies the receiving equipment itself. If specified, the receiving equipment receives the control data including its own address to control its associated terminals based on the received data. A control system of this kind is disclosed, for example, in Japanese Patent Application Laid-Open No. 2363/76 laid open on Jan. 9, 1976. Thus, in the prior art, the addresses which are not used for control have been also transmitted. As a result, the amount of information to be transmitted and received is large and the performance of transmission is degraded.